The role of hydrogeological and geochemical trapping in sedimentary basins for secure geological storage of carbon dioxide

TLDR

Sedimentary basins, which host fossil fuels, can store CO₂ securely in hydrogeological traps such as stratigraphic, structural, and hydrodynamic formations, where buoyancy, water density, lithology, and mineralogy govern long‑term solubility and mineral trapping. Each potential CO₂ storage site requires a risk analysis to assess trapping security.

Abstract

Abstract Sedimentary basins throughout the world are thick piles of lithified sediments that, in many cases, are the hosts for fossil fuel resources. They may become even more important in the future if they are used for the storage of anthropogenic carbon dioxide. The efficiency of CO 2 geological storage is determined by the structure of the sedimentary basins, which have an intricate plumbing system defined by the location of high and low permeability strata that control the flow of fluids throughout the basin and define ‘hydrogeological’ traps. The most secure type of hydrogeological trapping is found in ‘stratigraphic’ and ‘structural’ traps in oil and gas reservoirs that have held oil and gas for millions of years. Another form of hydrogeological trapping is ‘hydrodynamic’ trapping which has been recognized in saline aquifers of sedimentary basins that have extremely slow flow rates. A volume of carbon dioxide injected into a deep hydrodynamic trap may take millions of years to travel by buoyancy forces updip to reach the surface before it leaks back into the atmosphere. Moreover, as the carbon dioxide migrates towards the surface, it dissolves in the surrounding brine (‘solubility’ trapping) and may react geochemically with rock minerals to become permanently trapped in the sedimentary basin by ‘ionic’ or ‘mineral’ trapping. The efficiency of the CO 2 geological storage in sedimentary basins depends on many factors, among the most important being CO 2 buoyancy, formation water density, lithological heterogeneity and mineralogy. A risk analysis must be completed for each site chosen for the geological storage of CO 2 to evaluate the trapping security.